8 results on '"Hadi Parsamehr"'
Search Results
2. Formation of a single quasicrystal upon collision of multiple grains
- Author
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Ashwin J. Shahani, Sharon C. Glotzer, Insung Han, Z. Xi, Xianghui Xiao, Kelly L. Wang, Andrew T. Cadotte, and Hadi Parsamehr
- Subjects
Coalescence (physics) ,Condensed Matter - Materials Science ,Multidisciplinary ,Materials science ,Misorientation ,Condensed matter physics ,Science ,General Physics and Astronomy ,Quasicrystal ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Chemistry ,Article ,General Biochemistry, Genetics and Molecular Biology ,Molecular dynamics ,Phase transitions and critical phenomena ,Structure of solids and liquids ,Grain boundary ,Crystallite ,Thin film ,Translational symmetry - Abstract
Quasicrystals exhibit long-range order but lack translational symmetry. When grown as single crystals, they possess distinctive and unusual properties owing to the absence of grain boundaries. Unfortunately, conventional methods such as bulk crystal growth or thin film deposition only allow us to synthesize either polycrystalline quasicrystals or quasicrystals that are at most a few centimeters in size. Here, we reveal through real-time and 3D imaging the formation of a single decagonal quasicrystal arising from a hard collision between multiple growing quasicrystals in an Al-Co-Ni liquid. Through corresponding molecular dynamics simulations, we examine the underlying kinetics of quasicrystal coalescence and investigate the effects of initial misorientation between the growing quasicrystalline grains on the formation of grain boundaries. At small misorientation, coalescence occurs following rigid rotation that is facilitated by phasons. Our joint experimental-computational discovery paves the way toward fabrication of single, large-scale quasicrystals for novel applications., Quasicrystals exhibit long-range order without periodicity. The authors report an approach for quasicrystal fabrication and show through in situ imaging and corresponding simulations the formation of a single decagonal quasicrystal arising from coalescence of multiple quasicrystals in a liquid.
- Published
- 2021
3. Dynamic Observation of Dendritic Quasicrystal Growth upon Laser-Induced Solid-State Transformation
- Author
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L. Tang, Matthew J. Kramer, Joseph T. McKeown, Ashwin J. Shahani, Ying-Rui Lu, Z. Xi, Hadi Parsamehr, Cai-Zhuang Wang, and Insung Han
- Subjects
Quenching ,Materials science ,Icosahedral symmetry ,Intermetallic ,General Physics and Astronomy ,Quasicrystal ,01 natural sciences ,Condensed Matter::Materials Science ,Transmission electron microscopy ,Chemical physics ,Metastability ,0103 physical sciences ,Cluster (physics) ,010306 general physics ,Structural motif - Abstract
We report the laser-induced solid-state transformation between a periodic ``approximant'' and quasicrystal in the Al-Cr system during rapid quenching. Dynamic transmission electron microscopy allows us to capture in situ the dendritic growth of the metastable quasicrystals. The formation of dendrites during solid-state transformation is a rare phenomenon, which we attribute to the structural similarity between the two intermetallics. Through ab initio molecular dynamics simulations, we identify the dominant structural motif to be a 13-atom icosahedral cluster transcending the phases of matter.
- Published
- 2020
4. Mechanical and surface properties of Aluminum-Copper-Iron quasicrystal thin films
- Author
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Chih-Huang Lai, Shou-Yi Chang, and Hadi Parsamehr
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,Quasicrystal ,02 engineering and technology ,Nanoindentation ,021001 nanoscience & nanotechnology ,01 natural sciences ,Copper ,Contact angle ,Crystallography ,Crystallinity ,chemistry ,Mechanics of Materials ,Aluminium ,0103 physical sciences ,Materials Chemistry ,Composite material ,Thin film ,0210 nano-technology - Abstract
We show quasicrystal formation by annealing multilayers of Al, Cu and Fe. The mechanical and surface properties of quasicrystals are affected by the parameters of annealing process. Here, multilayer Al-Cu-Fe thin film samples with different compositions were sputtered on Si/SiO2 substrates and subjected to a two-step annealing process for different durations (5, 10 and 15 h). X-ray diffraction analyses indicated that the 15-h annealed sample had a sharper quasicrystal peak, which was more stable than any other phases. From the XRD data, the amount of each phase was calculated; the sample with longer annealing duration revealed a high amount of ψ-phase (84.3% crystallinity of quasicrystal) with a small amount of cubic Al50 (CuFe) 50 phase. Nanoindentation tests and contact angle measurements showed that this sample also had the greatest hardness (∼11 GPa) and the highest contact angle (127°), respectively.
- Published
- 2018
5. In-Situ observation of local atomic structure of Al-Cu-Fe quasicrystal formation
- Author
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Tzu-Ying Lin, An Pang Tsai, Ying Jiu Lu, Chih-Huang Lai, and Hadi Parsamehr
- Subjects
0301 basic medicine ,Diffraction ,Phase transition ,X-ray absorption spectroscopy ,Multidisciplinary ,Materials science ,Absorption spectroscopy ,Coordination number ,lcsh:R ,Analytical chemistry ,Quasicrystal ,lcsh:Medicine ,Article ,Nanomaterials ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,Phase (matter) ,lcsh:Q ,lcsh:Science ,030217 neurology & neurosurgery - Abstract
The phase and local environment, neighbouring atoms and coordination numbers (CN), for an Al-Cu-Fe multilayer were studied during heating (to 800 °C) and cooling (to room temperature) processes using in-situ X-Ray diffraction (XRD) and in-situ X-ray absorption spectroscopy (XAS) techniques to investigate the formation of Al-Cu-Fe quasicrystals (QCs). In-situ XRD clarified the transition of the ω-Al7Cu2Fe phase to a liquid state at the high temperature which transformed into the QC phase during cooling. The in-situ XAS showed a relatively small shift in distance between Cu-Al and Fe-Al during the phase evolution from RT to 700 °C. The distance between Cu-Cu, however, showed a significant increase from ω-phase at 700 °C to the liquid state at 800 °C, and this distance was maintained after QC formation. Furthermore, the CN of Fe-Al was changed to N = 9 during cooling. Through our observations of changes in CN, atomic distances and the atomic environment, we propose the local structural ordering of the quasicrystalline phase originated from a liquid state via ω-phase. In this study, we give a clear picture of the atomic environment from the crystalline to the quasicrystalline phase during the phase transitions, which provides a better understanding of the synthesis of functional QC nanomaterials.
- Published
- 2019
6. Thermal Spray Coating of Al-Cu-Fe Quasicrystals: Dynamic Observations and Surface Properties
- Author
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An Pang Tsai, Ding-Shiang Wang, Ashwin J. Shahani, Chen Tai-Sheng, Ming-Sheng Leu, Chih-Huang Lai, Hadi Parsamehr, and Insung Han
- Subjects
Contact angle ,Materials science ,Coating ,Annealing (metallurgy) ,Phase (matter) ,engineering ,Deposition (phase transition) ,Thermal stability ,Wetting ,engineering.material ,Composite material ,Thermal spraying - Abstract
In this study, we prepared Al-Cu-Fe quasicrystals (QCs) via thermal spray coating after optimizing the process parameters. Both in-situ XRD and in-situ TEM were used to investigate the thermal stability of QC phase. These dynamic techniques uniquely allow for a direct observation of QC growth upon heating and cooling. We show that the cubic s-Al-Cu-Fe is the dominant phase at room temperature (initial stage), but with an increase in temperature, the QC takes over at 650°C, consistent with thermodynamic calculations. Further increasing the temperature to 800°C, the QC phase transforms into cubic s-Al-Cu-Fe such that the s-Al-Cu-Fe phase is the only phase in existence at 870°C. Based on this result, we annealed the sample after thermal spray deposition for one hour at 650°C, which yielded an almost pure QC coating. The contact angle (against water) before annealing was 50°±4° but improved dramatically to 130°±5° after annealing at 650°C for one hour. This study provides a better understanding of QC formation during heat treatment as well as that of other secondary phases. Furthermore, these results can be used to manufacture QC coatings with enhanced interfacial properties that are central to technological applications.
- Published
- 2019
7. Direct Observation of Growth and Stability of Al-Cu-Fe Quasicrystal Thin Films
- Author
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Wei Ting Liu, Chih-Huang Lai, Shou-Yi Chang, Hadi Parsamehr, An Pang Tsai, Lih-Juann Chen, Shi Wei Chen, and Chun-Liang Yang
- Subjects
010302 applied physics ,Diffraction ,Materials science ,Polymers and Plastics ,Condensed matter physics ,Scattering ,Metals and Alloys ,Quasicrystal ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Synchrotron ,Electronic, Optical and Magnetic Materials ,law.invention ,Momentum ,Transmission electron microscopy ,law ,0103 physical sciences ,Ceramics and Composites ,Phason ,Thin film ,0210 nano-technology - Abstract
Al-Cu-Fe based quasicrystal thin films exhibit unique surface and mechanical properties. To better understand the formation of the quasicrystal thin films, we observe direct growth of quasicrystals, prepared in a multilayer Al-Cu-Fe thin films with subsequent heat treatment, by in-situ synchrotron x-ray diffraction and in-situ transmission electron microscopy during heating and cooling. Using these two methods, we show that the ternary phase is more thermodynamically stable compared to the binary phases at temperature higher than 470 °C during the heating process, and quasicrystal formation occurs during the cooling process, specifically at 660 °C, after the sample has reached a liquid state. To distinguish quasicrystal from approximant crystals in the obtained thin film samples, we use high resolution x-ray diffraction to analyze the sample at room temperature. We reveal that the peak broadening increases monotonically along the twofold, threefold, and fivefold high-symmetry directions with the physical scattering vector but does not have systematic dependence on the phason momentum, which suggests that the thin film sample is indeed a quasicrystal instead of approximant crystals and it is almost free of phason strain. Our study provides a complete understanding of the growth mechanism for thin film Al-Cu-Fe quasicrystals, which is of particular importance for developing versatile applications of quasicrystal thin films.
- Published
- 2019
8. Thermal spray coating of Al-Cu-Fe quasicrystals: Dynamic observations and surface properties
- Author
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Tai Sheng Chen, An Pang Tsai, Ashwin J. Shahani, Ming Sheng Leu, Insung Han, Z. Xi, Ding Shiang Wang, Hadi Parsamehr, and Chih-Huang Lai
- Subjects
010302 applied physics ,Materials science ,Annealing (metallurgy) ,Quasicrystal ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,01 natural sciences ,Contact angle ,Thermal spray coating ,Coating ,0103 physical sciences ,engineering ,General Materials Science ,Thermal stability ,Wetting ,Composite material ,0210 nano-technology ,Thermal spraying - Abstract
In this study, we prepared Al-Cu-Fe quasicrystals (QCs) via thermal spray coating after optimizing the process parameters. Both in-situ XRD and in-situ TEM were used to investigate the thermal stability of QC phase. These dynamic techniques uniquely allow for a direct observation of QC growth upon heating and cooling. We show that the cubic β-Al-Cu-Fe is the dominant phase at room temperature (initial stage), but with an increase in temperature, the QC takes over at 650 °C, consistent with thermodynamic calculations. Further increasing the temperature to 800 °C, the QC phase transforms into cubic β-Al-Cu-Fe such that the β-Al-Cu-Fe phase is the only phase in existence at 870 °C. Based on this result, we annealed the sample after thermal spray deposition for one hour at 650 °C, which yielded an almost pure QC coating. The contact angle (against water) before annealing was 50°±4° but improved dramatically to 130°±5° after annealing at 650 °C for 1 h. This study provides a better understanding of QC formation during heat treatment as well as that of other secondary phases. Furthermore, these results can be used to manufacture QC coatings with enhanced interfacial properties that are central to technological applications.
- Published
- 2019
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